As an example of a prior-art apparatus, there is one disclosed in, for example, JP-A-2002-27779 (termed “Patent Document 1”). The example stated in Patent Document 1 has a configuration wherein, as shown in FIG. 1 of the document, a second power source is disposed between the neutral point of a multiphase motor and the bus of the negative electrodes of an inverter, whereby even in the case of an abnormality in which one phase of the motor or the inverter has been disconnected, a motor torque can be outputted, and a torque ripple can be made small.
Besides, as another prior-art example, there is one wherein, as stated in JP-A-10-181617 (termed “Patent Document 2”), a second power source is not disposed between the neutral point of a multiphase motor and the bus of the negative electrodes of an inverter, and an abnormality in which one phase of the motor or the inverter has been disconnected is coped with by making the magnitude of a drive current smaller than in a normal mode, so as to output a motor torque smaller than in the normal mode.
Further, as another prior-art example, there is one wherein, as stated in JP-A-2003-26020 (termed “Patent Document 3”), a second power source is not disposed between the neutral point of a multiphase motor and the bus of the negative electrodes of an inverter, and even in the case of an abnormality in which one phase of the motor or the inverter has been disconnected, an ordinary control method is continued, thereby to output a motor torque. A “dq” control is the commonest as the ordinary control method.
Patent Document 1: JP-A-2002-27779
Patent Document 2: JP-A-10-181617
Patent Document 3: JP-A-2003-26020